Theory of diffusion-controlled reactions: Formulation of the bulk reaction rate in terms of the pair probability

1983 ◽  
Vol 21 (1-2) ◽  
pp. 167-175 ◽  
Author(s):  
M. Tachiya
Keyword(s):  
Reaction Rate ◽  
Pair Probability ◽  
Diffusion Controlled ◽  
Bulk Reaction

Investigation of chlorine wall decay in an old, decommissioned metallic pipe using a pipe section reactor

2020 ◽  
Vol 20 (3) ◽  
pp. 953-962
Author(s):  
R. Tonev ◽  
G. Dimova
Keyword(s):  
Reaction Rate ◽  
Rate Coefficient ◽  
Tap Water ◽  
Decay Rates ◽  
Free Chlorine ◽  
Reaction Rate Coefficient ◽  
Pipe Section ◽  
Reaction Coefficient ◽  
Bulk Reaction ◽  
Series Of Experiments

Abstract The study investigates the kinetics of free chlorine depletion in tap water from the Sofia distribution network. The overall decay rates, the bulk reaction rate coefficient, the wall reaction rate coefficient and the influence of mass transfer have been determined in a laboratory pipe section reactor (PSR), testing an old decommissioned metallic pipe. In total, 23 series of experiments were performed under different initial free chlorine concentrations and different hydraulic conditions. The applicability of different chlorine decay mathematical models has been investigated. A new model was proposed, combining zero order bulk reactions and first order wall reactions, describing the laboratory results with Nash-Sutcliffe efficiency coefficients over 0.99. The obtained values for the wall reaction coefficient vary in the range 0.008–0.030 m/h, decreasing exponentially with increasing initial chlorine concentration.

Hydrogen Recombiner: Theoretical Parametric Study

2002 ◽  
Author(s):  
Gilles Avakian
Keyword(s):  
Hydrogen Concentration ◽  
Total Pressure ◽  
Reaction Rate ◽  
Published Data ◽  
Geometrical Parameters ◽  
Surface Kinetics ◽  
Total Rate ◽  
Diffusion Controlled ◽  
Rate Of Reaction ◽  
Linear Behaviour

There is not yet published data concerning a complete overview of the behaviour of a SIEMENS recombiner versus the thermal hydrualic conditions and the geometry of the catalytic plates. This paper reports on a numerical behaviour of the recombiner depending on several gas parameters as the total pressure, and the hydrogen concentration, as well as geometrical parameters of the catalytic elements as the height and the spacing. We use a theoretical model validated by using the KALI experiments. In this model (Avakian, 1999), the reaction rate is diffusion-controlled, i.e. the contribution of surface kinetics to the total rate of reaction is neglected. We demonstrate a quasi-linear behaviour of the recombination rate vs. the total pressure and the hydrogen concentration. We display the benefit in using smaller catalytic plates instead of taller plates and we give an idea of the influence of the spacing between the catalytic plates.

scholarly journals Electrochemical Behavior of Malachite Green in Aqueous Solutions of Ionic Surfactants

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Mohammad Mijanur Rahman ◽  
M. Yousuf A. Mollah ◽  
M. Muhibur Rahman ◽  
Md. Abu Bin Hasan Susan
Keyword(s):  
Malachite Green ◽  
Electrochemical Behavior ◽  
Cetyltrimethylammonium Bromide ◽  
Reaction Rate ◽  
Surface Reaction ◽  
Sodium Dodecyl ◽  
Reaction Rate Constant ◽  
Carbon Electrode ◽  
Diffusion Controlled ◽  
Apparent Diffusion

Electrochemical behavior of malachite green (MG) oxalate in aqueous solution was studied in the presence of a cationic surfactant, cetyltrimethylammonium bromide (CTAB), and an anionic surfactant, sodium dodecyl sulfate (SDS) at a glassy carbon electrode using cyclic voltammetry. The electrochemical oxidation of MG has been characterized as an electrochemically irreversible diffusion-controlled process. Oxidative peak current sharply decreased with increasing SDS concentration, while a slight increase with increasing [CTAB] was apparent. The apparent diffusion coefficient, the surface reaction rate constant, and the electron transfer coefficient of MG clearly show correlation of the electrochemical behavior with the dissolved states of the surfactants. Electrochemical observations together with spectrophotometric results at varying surfactant concentrations provide evidence of interaction of MG with the surfactants to varying extent depending on the type of the surfactant and the concentration.

Picoliter enzyme reactor on a nanofluidic device exceeding the bulk reaction rate

The Analyst ◽  
2020 ◽  
Vol 145 (17) ◽  
pp. 5801-5807 ◽  
Author(s):  
Koki Yamamoto ◽  
Kyojiro Morikawa ◽  
Hiroyuki Imanaka ◽  
Koreyoshi Imamura ◽  
Takehiko Kitamori
Keyword(s):  
Reaction Rate ◽  
Enzyme Reactor ◽  
Bulk Reaction ◽  
Nanofluidic Device

A picoliter enzyme reactor using a trypsin immobilized nanochannel realized 25 times faster reaction than the bulk reaction.

Diffusion Controlled Effective Reaction Rate for a Surface Reaction with Orientational Selectivity

1978 ◽  
Vol 33 (11) ◽  
pp. 1243-1250
Author(s):  
Siegfried Hess
Keyword(s):  
Continued Fraction ◽  
Reaction Rate ◽  
Surface Reaction ◽  
Reaction Plane ◽  
Special Choice ◽  
Continued Fraction Expansion ◽  
Diffusion Controlled ◽  
Nonspherical Molecules ◽  
Effective Reaction ◽  
Effective Reaction Rate

The influence of the orientational selectivity of a chemical reaction on the diffusion controlled effective reaction rate is investigated theoretically for the following situation: Nonspherical molecules with random orientation are put into a chemically inert solution at a plane which is a certain distance away from the parallel reaction plane. The reaction frequency at the surface shall depend on the orientation of the figure axis of a molecule relative to the normal of the reaction plane. With a special choice for the orientational dependence of the surface reaction, a continued fraction expansion is derived for the diffusion controlled effective reaction rate. This quantity is discussed and displayed graphically as function of the relevant parameters.

The silver(I)-copper reaction in acetonitrile-water mixtures

1984 ◽  
Vol 37 (5) ◽  
pp. 903 ◽  
Author(s):  
FJ Hughes ◽  
IM Ritchie ◽  
P Singh
Keyword(s):  
Reaction Rate ◽  
Rotation Speed ◽  
Kinetic Studies ◽  
Polarization Curves ◽  
Limiting Current ◽  
Slow Step ◽  
Surface Roughening ◽  
Kinetic Rate ◽  
Diffusion Controlled ◽  
Good Agreement

An electrochemical and kinetic study of the silver(I)-copper displacement (cementation) reaction in acidified acetonitrile-water mixtures is reported. The cathodic polarization curves for the reduction of silver(I) were found to be those of a fast electrochemical reaction. From the variation of limiting current with rotation speed, the diffusion coefficient of silver(I) as a function of acetonitrile concen- tration was determined. The anodic oxidation of copper gave a Tafel slope of 60 mV per decade of current and was rotation-speed-dependent. It is suggested that the slow step in the reaction mechanism is the diffusion of copper(I) from the electrode surface. At all acetonitrile concentrations investigated, the two polarization curves intersected at a point where the current is fixed by the diffusion of silver(I); this suggests that the displacement reaction will be diffusion-controlled, which was confirmed by kinetic studies. Provided the silver deposit was not too thick, there was good agreement between the measured kinetic rate and that calculated from the silver(I) limiting-current measurements. However, when the deposit became too thick, some increase in reaction rate due to surface roughening was observed.

scholarly journals Positronium in a Liquid Phase: Formation, Bubble State and Chemical Reactions

2012 ◽  
Vol 2012 ◽  
pp. 1-17 ◽  
Author(s):  
Sergey V. Stepanov ◽  
Vsevolod M. Byakov ◽  
Dmitrii S. Zvezhinskiy ◽  
Gilles Duplâtre ◽  
Roman R. Nurmukhametov ◽  
...  
Keyword(s):  
Energy Deposition ◽  
Reaction Rate ◽  
Local Heating ◽  
Bubble Radius ◽  
Annihilation Rate ◽  
Electron Pairs ◽  
Reaction Rate Constants ◽  
Slowing Down ◽  
Diffusion Controlled ◽  
Different Temperatures

The present approach describes the e+ fate since its injection into a liquid until its annihilation. Several stages of the e+ evolution are discussed: (1) energy deposition and track structure of fast positrons: ionization slowing down, number of ion-electron pairs, typical sizes, thermalization, electrostatic interaction between e+ and the constituents of its blob, and effect of local heating; (2) positronium formation in condensed media: the Ore model, quasifree Ps state, intratrack mechanism of Ps formation; (3) fast intratrack diffusion-controlled reactions: Ps oxidation and ortho-paraconversion by radiolytic products, reaction rate constants, and interpretation of the PAL spectra in water at different temperatures; (4) Ps bubble models. Inner structure of positronium (wave function, energy contributions, relationship between the pick-off annihilation rate and the bubble radius).

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